A typical example of a traditional three part package is a tin can, which is soldered and/or folded together of plate. The ordinary can is cylindrical and is thus manufactured of a rolled rectangular barrel, a circular cover and a circular bottom. A tin can is normally not exposed to any substantial internal overpressure, which means that the cover and the bottom can be generally planar.
A bottom design for a cylindrical package is shown in U.S. Pat. No. 4,023,700. This design enables the package to be exposed for an internal overpressure. The material in the package is thin aluminium, which at least internally is coated with polyethylene type HD, which enables a sealing. The bottom has a dome, which faces downward and whose circular outer edge is folded to a rim, which by heating can be melt connected to the cylindrical barrel of the package. For preventing the internal overpressure from creating a force for splitting up the package between the barrel and the bottom the space around the dome at its outside against the barrel is filled with thermoplastic foam. A further reinforcement can be accomplished by means of an adhesive band around the package on its outside.
It goes without saying that such a design leads to high material and manufacturing costs and adds to the weight of the package, which is an important negative factor.